1. Field of the Invention
The present invention relates to an apparatus and a method for matching a fingerprint.
2. Description of the Related Art
Recently, computers have been installed in various systems with identification equipment attracting much attention. Conventionally, an ID card or a password have been used as an authentication measure. However, they have many problems in security.
As an authentication measure more reliable than a password, a personal matching technique using biometric information has attracted much attention. When a user can be checked using biometric information unique to the user, the check result is very reliable.
One of the biometric information available in authenticating a user is a fingerprint. A fingerprint is said to have two features, that is, ‘uniqueness’ and ‘invariability’, and is an expected authentication measure. Some research and development have been performed on a personal matching system using a fingerprint these days.
The biometric information to be used in authenticating a user can be a fingerprint, a voiceprint, an iris, a vein network on the retina, a signature, etc. They can be measured by various sensors such as a CCD camera, etc., and converted into electronic information such as an image, etc. Then, various information processes are performed on the biometric information obtained by a sensor, and the information for identifying a user is extracted from biometric information. A user can be authenticated by matching the biometric key information with preliminarily registered biometric key information about each user.
A fingerprint can be considered as practical biometric information.
The surface of a person's finger is not smooth. Raised lines are called ridges. Ridges form various patterns unique to a person. Ridges have bifurcation points and ending points. Since each person has his or her own distribution of bifurcation points and ending points, these points are referred to as feature points of a fingerprints. The distribution of feature points are used as an important measure for specifying a person. When a fingerprint matching process is performed, the position, type, direction of these feature points are checked to determine whether or not a fingerprint matches a reference fingerprint.
The conventional fingerprint matching process has been performed by checking the length of ridges between feature points (refer to, for example, the Japanese Laid-Open Patent Publication No.11-195119). However, it is not sufficient in some cases to check only the lengths of ridges. Therefore, it is expected to improve the performance of the fingerprint matching process. In the previous method, the data of the lengths of ridges is stored as a part of fingerprint data, but is hard to be stored efficiently. That is, the size of the fingerprint data tends to be larger.